Honda F501 Owner's Manual page 44

4. Spark plug service
Recommended spark plug:
To ensure proper engine operation, the spark plug must be properly
gapped and free of deposits.
1. Remove the spark plug cap.
Use the spark plug wrench to remove the spark plug.
If the engine has been running, the muffler will be very hot. Be careful
not to touch the muffler.
SPARK PLUG CAP
Visually inspect the spark plug. Discard it if the insulator is cracked
2.
or chipped. Clean the spark plug with a wire brush if it is to be
reused.
3. Measure the plug gap with a
feeler gauge.
Correct as necessary by
bending the side electrode.
The gap should be:
0.7 0.8 mm (0.028 0.031 in) −
BPR5ES (NGK)
W16EPR-U (DENSO)
−
SPARK PLUG WRENCH
0.7 0.8 mm −
(0.028 0.031 in) −
41